1. Field of the Invention
The present invention generally relates to a post-treatment method which is carried out after dry etching, and more specifically, it relates to a post-treatment method for dry etching, which is improved to be capable of completely removing a deposit resulting from the dry etching.
2. Description of the Background Art
In relation to semiconductor fabrication steps, there are number of steps of dry-etching various wiring materials through resist masks.
FIGS. 9A to 9C are sectional views showing a conventional method of forming a wiring pattern or an electrode pattern.
Referring to FIG. 9A, a wiring layer (or an electrode material layer) 7 is formed on an underlayer oxide film 8 which is formed on a wafer (not shown). A resist pattern 16 having a prescribed shape is formed on the wiring layer 7.
Referring to FIGS. 9A and 9B, the wiring layer 7 is dry-etched through the resist pattern 16 serving as a mask. At this time, a deposit 9 is formed along side walls of the resist pattern 16. This deposit 9 is formed by a mixture of material components of the wiring layer 7, a gas employed for the etching, and organic components of the resist pattern 16.
Referring to FIGS. 9B and 9C, the resist pattern 16 is removed by ashing employing an oxygen plasma or the like. At this time, the deposit 9 remains unremoved after the ashing. The deposit 9 causes short-circuiting or leakage across a wire and breaking of a contact part to extremely deteriorate performance of a semiconductor device, if the same is left intact.
In general, the deposit 9 is removed through a cleaning liquid, which is selected in response to the wiring material or the material for an electrode part.
As hereinabove described, the cleaning liquid is varied with the wiring material or the material for an electrode part.
When the wiring material is prepared from WSi or poly-Si, an aqueous ammonia hydrogen peroxide solution (APM) or an aqueous hydrogen fluoride solution is employed as the cleaning liquid. When the wiring material contains Al, this material is also etched in a large quantity if an aqueous acidic or alkaline solution is employed as the cleaning liquid. In order to avoid this, a cleaning liquid containing an organic solvent such as organic amine is employed in this case. However, this cleaning liquid also etches the wiring material (7) while removing the deposit 9. In general, the wiring layer 7 is disadvantageously extremely etched when a cleaning liquid which can readily remove the deposit 9 is employed. In formation of a fine wiring pattern, therefore, it is difficult to employ the aforementioned cleaning liquid.
When a capacitor is prepared from a high dielectric material, on the other hand, its electrode is prepared from a metal material having a high melting point, such as Pt having small reactivity, in particular. Thus, the deposit 9 inevitably contains Pt, and hence it is difficult to remove this deposit 9 through a chemical liquid. While the deposit 9 can be removed through aqua regia, the electrode material (7) is also etched in this case. In formation of a fine electrode pattern, therefore, it is difficult to employ this method.
While there has also been proposed a cleaning method employing high pressure injection (a jet scrubber), the detergency is so small that the deposit 9 cannot be completely removed.